Two-way door latching mechanisms are well known in the art. Typically doors are opened and closed today by means of a lockset which includes both a manipulatable handle or knob for moving the door and also for engaging a latching mechanism. A lockset generally includes an interior knob (or handle) and an exterior knob (or handle) which are connected by a spindle. Rotating either knob rotates the spindle, allowing it to catch and engage a latch mechanism. The latch mechanism includes a cylinder perpendicular to the spindle, and turning a knob pulls the cylinder in the direction of the turn. The free end of the cylinder is the latch, extending out from the door's edge and into an opening in the opposing door frame or door jamb. When the door is closed the latch is engaged with the opposing door frame and the door cannot be opened. Rotating the knob, spindle and cylinder retracts the latch from its position in the door frame opening, allowing the door to be opened. Where the knob is a handle, the handle itself may rotate, or it can include a levering means, typically a depressable lever, that rotates the attached spindle.
Another well-characterized two-way door latching mechanism involves a liftable latch arm and latch keep on the surface of the inside side of the door, and a means for lifting the latch arm on the surface of the outside side of the door. Traditionally the outside lifting means is an elongated bar, called a thumb lever, that passes through the door and on which the latch arm rests. When one end of the thumb lever bar is depressed on the outside of the door, the other end of the bar is lifted, lifting the latch arm with it, past the latch keep, and allowing the door to open.